1. Field of the Invention
The present invention relates to a substrate processing apparatus having a heat treatment unit, a solution processing unit, and a conveying unit.
2. Description of the Related Art
In a photoresist process of a semiconductor device fabrication, resist solution is coated to a substrate such as a semiconductor wafer (hereinafter referred to as wafer). The resist film is exposed so that a predetermined pattern is formed. The resultant wafer is developed with developing solution. To do these processing steps, a coating and developing apparatus has been used.
The coating and developing apparatus has a heat treatment unit and a solution process unit. The heat treatment unit performs a hydrophobic process for improving the adhesion of for example resist, a heating process for heating a wafer coated with resist solution and for hardening the resist film, and a cooling process for cooling a heated wafer. The solution process unit is for example a resist coating unit or a developing process unit. The resist coating unit coats resist solution to a wafer and forms a resist film. The developing process unit develops an exposed wafer with developing solution. A wafer is conveyed from the heat treatment unit to the solution process unit by a conveying unit. The conveying unit has for example three pincettes that are disposed at an upper position, a middle position, and a lower position of the conveying unit (hereinafter, these pincettes are referred to as upper pincette, middle pincette, and lower pincette). The conveying unit loads/unloads a wafer to/from the heat treatment unit or the solution process unit while holding the wafer with these pincettes.
The upper pincette is used for the conveying unit to unload a wafer from the resist coating unit. The middle and lower pincettes are used for the conveying unit to load/unload a wafer to/from the heat treatment unit. In such a structure, a wafer unloaded from the resist coating unit is not affected by heat of the pincette. Thus, the film thickness of a resist film that is sensitive against temperature can be prevented from varying.
However, when the diameter of a wafer becomes large, the amount of heat stored in the wafer becomes large. Thus, the amount of heat applied to the middle and lower pincettes is larger than that of a smaller diameter wafer. Consequently, the influence of the heat radiation of the middle and lower pincettes against the upper pincette cannot be ignored. In other words, the heat radiation causes the upper pincette to heat up. Thus, the film thickness of the resist film of the wafer held by the upper pincette may vary. To solve such a problem, for example, a heat insulating plate is disposed in a space between the upper pincette in and the middle pincette.
However, the space between the upper pincette and the middle pincette is narrow, and therefore it is difficult to dispose the heat insulating plate in such a space. In addition, when the heat insulating plate is disposed in the space, the conveying unit becomes large and complicated.